You may have heard people say, ‘If you hear frogs, it’s a healthy environment.’
This is true for a number of reasons, particularly because of the way frogs breathe and drink through their skin, which makes them very sensitive to water and soil quality. Frogs also congregate in areas of higher plant diversity, meaning they indicate overall biodiversity. During breeding season, frog spawn can be seen covering water surfaces, and when the tadpoles hatch, they graze on algae and detritus. Therefore, tadpoles limit abundance of algae in wetlands, and they also transfer energy up wetland flood plains, as they are eaten by predators such as water birds.
Because frogs sit in the middle of the food chain, they are a key link system, sustaining the wider wetland ecosystem. In this way, not only do frogs choose healthy environments to live in, but they also help keep environments functioning at their best health. They are an incredibly valuable part of the ecosystem and it’s worth ensuring we help to maintain their population.
Some Types of Frogs You May Hear Around Anglesea:
Limnodynastes dumerilii—Eastern Banjo Frog/Pobblebonk Frog
You would have heard the Pobblebonk frog around Coogoorah park, from its distinctive ‘bonk, bonk, bonk.’ A large, burrowing frog, the Pobblebonk frog is also quite recognisable by its size, reaching up to 70 mm. This is a common and widespread species and can often be seen in large numbers at night, especially after rain. Its scientific name, Limnodynastes dumerilii, means ‘Lord of the Swamp.’
Eastern Banjo Frog
Litoria ewingii—The Southern Brown Tree Frog
These frogs are agile climbers and jumpers and are typically found in flooded grasslands or marshes, making the swamp areas of Anglesea a great habitat for them. This frog is an insectivore and can leap to catch flies in mid-air, a typical trait of tree frogs. Their call sounds like ‘cree, cree-cree-cree.’
Southern Brown Tree Frog
Crinia signifera—Common Eastern Froglet
This is a small ground dwelling frog found mostly throughout Victoria, including the Surf Coast. Usually found around water, the males call from the shallows all year round and can be heard at any time of the day. A low pitched, mechanical croak; ‘crick, crick, crick, crick.’ In terms of conservation status, this frog species is secure.
Common Eastern Froglet
Litoria raniformis—Growling Grass Frog
The Growling Grass Frog is the largest frog in the local district and has a distinctive warty back. It is currently listed as endangered and the population is declining. They favour water ways which hold water for at least six months of the year. Their call sounds like; ‘grrruh-uh-uh-urk, grrruh-uh-uh-urk.’
Growling Grass Frog
Habitat, Water Quality and What We Can Do to Manage Both
Frogs are more drawn to shallow waterbodies, as males sit in the shallows to call and females lay their eggs. Some breeds of frogs, including the Growling Grass Frog, are not as particular with where they congregate and can be found along water pipes and drains too. Habitats with dense surrounding vegetation, particularly with a variety of plant species, are more favourable, as this means all-round diversity of bugs and organisms to feed off.
Habitat and water can be disrupted when storm water and runoff enter marshes and swamps. Frogs breathe and drink through their skin, so a slight change in water quality and salinity can cause them to die. Many scientific studies have shown how the embryonic and larval stages of frogs are particularly vulnerable to saline conditions. This is because salt disrupts the ionic and water exchange across the permeable membranes of the larvae, blocking nutrition needed to develop.
A study carried out on the effects of salinity on the survival, growth and development of tadpoles and the Brown Tree Frog, Litoria ewingii, has shown that salinity of 16 per cent significantly decreases survival of tadpoles. Growth rate and mass slows significantly and the time taken to reach frog stage was prolonged. In saline conditions, most frog larvae are far less likely to survive, making the minority that do less healthy, with smaller chance of survival into adulthood. This is another reason why it is so important to prevent stormwater, sediment and pollutants leeching into waterways, as they can impact on saline levels, causing frog life to diminish.
Loss of connectivity between wetlands and larger waterbodies causes frog population to dwindle. This can occur as a result of dry periods, or removal of swamp and waterway vegetation. Integrating more varied species of indigenous wetland plants to increase overall diversity and invite more species of frogs can help with this. Creating vegetation corridors along drainage lines can help boost and spread frog populations. Growling Grass Frogs have been seen to breed along drainage lines, which is hopeful, considering the endangered state they are currently facing.
Some Extra Facts
- Frogs were the first ever land animals to evolve vocal cords
- Frogs use their eye balls to swallow food. They pull their eyes back into their mouths to push the food down into their stomach
- Only male frogs call. This is done to find a partner as well as to warn away other male competition
Article title: Salt Tolerance
Website title: Froglife.org https://www.froglife.org/tag/salt-tolerance/
Author: Kavitha Chinathamby Effects of Salinity on the Survival, Growth and Development of Tadpoles of the Brown Tree Frog, Litoria Ewingii http://www.publish.csiro.au/ZO/ZO06006